JP2015010143A - Ink for ink jet printing, method for producing ink for ink jet printing, and inkjet printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high glossiness printed matter by preventing the reduction in the gloss of a printed matter caused by ruggedness produced in the surface of an ink layer impacted on the medium to be recorded.SOLUTION: Provided is an ink for inkjet printing comprising a solvent and the grains of a binder resin dispersed or suspended into the solvent, and the grains of the binder resin include flat grains 1 in which at least one cross-section has an elliptical shape.

Description

  The present invention relates to an inkjet printing ink, a method for producing an inkjet printing ink, and an inkjet printing method.

  Patent Document 1 describes an ink containing an emulsion.

JP-A-9-87560 (published March 31, 1997)

  By the way, when a binder resin is produced by a conventional emulsion polymerization method, spherical binder resin particles are generated due to surface tension. When ink for inkjet printing containing spherical particles of such a binder resin lands on the recording medium, fine irregularities resulting from the shape of the binder resin particles are generated on the ink surface, and the glossiness of the printed matter decreases due to the irregularities. There is a problem of doing.

  The present invention has been invented in view of the above problems, and is an ink for ink jet printing that can prevent a decrease in gloss of a printed matter due to unevenness generated on the surface of the ink that has landed on a recording medium and can obtain a highly glossy printed matter. The manufacturing method and the printing method are provided.

  The ink for inkjet printing according to the present invention contains a solvent and particles of a binder resin dispersed or suspended in the solvent, and the particles of the binder resin include flat particles having at least one elliptical cross section. It is characterized by.

  According to the above configuration, the binder resin particles contained in the ink include flat particles having at least one elliptical cross section. Therefore, when such ink lands on the recording medium, the long axis, which is the longest diameter among the diameters passing through the center of gravity of the flat particles, is on the surface of the recording medium. Flat particles fall down. That is, in the ink layer formed on the recording medium, the flat particles are oriented so that their long axes are along the surface of the recording medium.

  For this reason, it is possible to reduce the level difference of the unevenness generated on the surface of the ink layer on the recording medium due to the shape of the particles of the binder resin. As a result, light scattering caused by unevenness on the surface of the ink layer can be reduced, so that a highly glossy printed matter can be obtained.

  In the ink for inkjet printing according to the present invention, the flat particles are preferably produced by an extension polymerization method.

  According to the above configuration, since the flat particles are produced by the extension polymerization method, an ink for inkjet printing including the flat particles that are preferably flattened can be obtained efficiently.

  In the ink for inkjet printing according to the present invention, the flat particle has a length of the longest diameter out of the diameter passing through the center of gravity of 1.5 to 15 times the length of the shortest diameter. It is preferable.

  According to the said structure, in the flat particle, the length of the long axis which is the longest diameter among the diameters which pass through the gravity center becomes sufficiently longer than the length of the short axis which is the shortest diameter. As a result, the flat particles in the ink that have landed on the recording medium easily fall on the recording medium, and the flat particles are easily oriented so that the long axis of the flat particles is along the surface of the recording medium. Accordingly, it is possible to more effectively reduce the level difference of the unevenness generated on the surface of the ink layer.

  In the ink for inkjet printing according to the present invention, the flat particles preferably include a colorant.

  According to the above configuration, since the colorant is encapsulated in the flat particles, aggregation of the colorant can be prevented, and ink storage stability and ejection stability can be improved.

  In the ink for inkjet printing according to the present invention, it is preferable that the flat particles further include particles of a binder resin having a metal plating layer on the particle surface and having no metal plating layer.

  According to the above configuration, a suitable metallic ink can be provided. In addition, since the flat particles provided with the metal plating layer are oriented along the surface of the recording medium, printing using such an ink can provide a printed matter with excellent concealment of the ink layer.

  The ink for inkjet printing according to the present invention preferably contains the flat particles in an amount of 20% by weight to 100% by weight with respect to the total amount of the binder resin particles.

  When the ink for inkjet printing contains the flat particles 1 with the content in the above range, the unevenness generated on the surface of the ink layer due to the shape of the particles of the binder resin even when the particles of the other binder resin are spherical. The height difference can be reduced.

  A method for producing an ink for ink-jet printing according to the present invention is a method for producing an ink for ink-jet printing containing a solvent and particles of a binder resin dispersed or suspended in the solvent. It includes a synthesis step for producing binder resin particles.

  According to the above configuration, since the particles of the flat binder resin can be suitably produced by the elongation polymerization method, the ink for inkjet printing capable of reducing the unevenness generated on the surface of the ink layer on the recording medium is obtained. It can manufacture suitably.

  The ink jet printing ink production method according to the present invention preferably further includes an electroless plating step of electrolessly plating the surface of the binder resin particles after the synthesis step.

  According to the said structure, a metal plating layer can be formed in the surface of the particle | grains of the flat binder resin produced by the extending | stretching polymerization method. Thereby, the metallic ink for inkjet printing can be manufactured suitably.

  The printing method according to the present invention is characterized by using any of the ink jet printing inks described above.

  According to the said structure, highly glossy printed matter can be obtained using the ink for inkjet printing which concerns on this invention.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that the height difference of the unevenness | corrugation which arises on the surface of an ink layer is reduced, and a highly glossy printed matter can be printed.

It is a figure explaining the outline | summary of the printed matter printed using the ink for inkjet printing which concerns on one Embodiment of this invention.

[Ink for inkjet printing]
Hereinafter, the present invention will be described in detail.

  The ink for inkjet printing according to the present invention contains a solvent and particles of a binder resin dispersed or suspended in the solvent, and the particles of the binder resin include flat particles having at least one elliptical cross section. An ink for inkjet printing according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating an outline of a printed matter printed using ink for inkjet printing according to an embodiment of the present invention.

  1A schematically shows the state of the flat particles 1 containing the colorant 2 in the ink layer 20 formed on the recording medium 10, and FIG. 1B shows the recording medium. 10 schematically shows an ink layer 20 formed on the substrate 10. The ink ejected from the inkjet nozzles lands on the recording medium 10 and forms an ink layer 20 on the recording medium 10 as shown in FIG. In the ink layer 20 formed on the recording medium 10, as shown in FIG. 1A, the flat particles 1 included in the binder resin particles in the ink are oriented.

  Here, in the ink for ink jet printing according to the present embodiment, since the flat particles 1 are elliptical in at least one cross section, the long axis which is the longest diameter among the diameters passing through the center of gravity is the recording target. The flat particles 1 fall on the recording medium 10 along the surface of the medium 10. That is, in the flat particles 1, the flat particles 1 are oriented on the recording medium 10 so that the short axis, which is the shortest diameter among the diameters passing through the center of gravity, intersects the surface of the recording medium 10.

  Therefore, as shown in FIGS. 1A and 1B, the difference in height of the unevenness caused by the shape of the binder resin particles generated on the surface of the ink layer 20 is reduced as compared with the case of the spherical binder resin particles. can do. As a result, irregular reflection of light on the surface of the ink layer 20 can be suppressed, and a highly glossy printed matter can be obtained.

  The flat particle 1 is obtained by flattening a sphere, and at least one cross section is an ellipse. The flat particles 1 may have an ellipsoidal shape. It is preferable that the length of the longest diameter of the flat particles 1 passing through the center of gravity thereof is 1.5 times or more and 15 times or less of the length of the shortest diameter, 2.0 times or more, More preferably, it is 10 times or less. When the degree of flatness (flatness) of the flat particles 1 is in the above range, the long axis length of the flat particles 1 is sufficiently longer than the short axis length. Thereby, the flat particles 1 in the ink that has landed on the recording medium 10 are likely to fall on the recording medium 10, and the flat particles 1 can be easily formed so that the long axis of the flat particles 1 is along the surface of the recording medium 10. Oriented to Accordingly, it is possible to more effectively reduce the level difference of the unevenness generated on the surface of the ink layer 20.

  The ink for inkjet printing may contain spherical particles in addition to the flat particles 1 as the particles of the binder resin, but the flat particles 1 are 20% by weight or more based on the total amount of the particles of the binder resin. The content is preferably 100% by weight or less, more preferably 30% by weight or more and 80% by weight or less. When the ink for inkjet printing contains the flat particles 1 with the content in the above range, the unevenness generated on the surface of the ink layer due to the shape of the particles of the binder resin even when the particles of the other binder resin are spherical. The height difference can be reduced.

  The flat particles 1 as described above may be produced by an extension polymerization method. Details of the extension polymerization method will be described later.

  In the ink for inkjet printing, as shown in FIG. 1 (a), the colorant 2 may be included in the flat particles 1, that is, in the binder resin particles, or dispersed in a solvent. Also good. Moreover, the ink for inkjet printing may contain both the colorant 2 included in the flat particles 1 and the colorant 2 dispersed in the solvent. Further, when the ink for inkjet printing is used as the clear ink, the colorant 2 may not be included.

  In the ink for inkjet printing, the binder resin particles may further include binder resin particles having a metal plating layer on the particle surface and no metal plating layer. Thus, the metallic ink for inkjet printing can be provided by providing a metal plating layer on the surface of the binder resin particles. Further, the flat particles 1 provided with the metal plating layer are oriented so that the long axis thereof is along the surface of the recording medium 10, and therefore the ink layer 2 is excellent in concealment by printing with such an ink. Printed material is obtained.

  Examples of the method for forming the metal plating layer on the surface of the binder resin particles include a method of electroless plating the surface of the binder resin particles. Details of the method of electroless plating the binder resin particles will be described later.

(Binder resin)
The binder resin particles are synthesized by an extension polymerization method. Binder resin particles can be obtained by radical polymerization of a monomer having an unsaturated double bond in the presence of a polymerization initiator.

  Examples of monomers used for the synthesis of binder resin particles by the extension polymerization method include (a) aromatic group-containing (meth) acrylate monomer (b) salt-forming group-containing monomer, (c) macromonomer, (d) hydrophobic And (e) a hydroxyl group-containing monomer, and (f) an oxyalkylene group-containing monomer. Although these monomers may be used independently, it is preferable that multiple types are included among (a)-(f), and it is more preferable that all types are included.

  Examples of (a) aromatic group-containing (meth) acrylate monomers include phenyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 1-naphthalyl acrylate, 2-naphthalyl (meth) acrylate, phthalimidomethyl (meth) acrylate, p-nitrophenyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2 -Acryloyloxyethyl phthalic acid etc. are mentioned.

  (B) As the salt-forming group-containing monomer, an anionic monomer and a cationic monomer are more preferably used. Examples of the anionic monomer include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.

  Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Examples of unsaturated sulfonic acid monomers include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Can be mentioned. Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl A phosphate etc. are mentioned.

  Examples of the cationic monomer include an unsaturated tertiary amine-containing vinyl monomer and an unsaturated ammonium salt-containing vinyl monomer.

  Examples of the unsaturated tertiary amine-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N. -Dimethylaminopropyl (meth) acrylamide, vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-6-vinylpyridine, 5-ethyl-2-vinylpyridine and the like. Examples of unsaturated ammonium salt-containing monomers include N, N-dimethylaminoethyl (meth) acrylate quaternized product, N, N-diethylaminoethyl (meth) acrylate quaternized product, N, N-dimethylaminopropyl (meth). Examples include acrylate quaternized products. Among the cationic monomers, N, N-dimethylaminoethyl (meth) acrylate, NN-dimethylaminopropyl (meth) acrylamide and vinylpyrrolidone are more preferable.

  The said (b) salt production | generation group containing monomer can be used individually or in combination of 2 or more types.

  (C) As a macromonomer, a styrenic macromonomer having a polymerizable functional group at one end, an alkyl (meth) acrylate macromonomer having a polymerizable functional group at one end, and a polymerizable functional group at one end The silicone macromonomer having is preferably used. The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, and by copolymerizing these, a binder resin having a structural unit derived from a macromonomer can be obtained. The styrene macromonomer having a polymerizable functional group at one end includes a styrene homopolymer having a polymerizable functional group at one end, and a copolymer of styrene and another monomer having a polymerizable functional group at one end. Coalescence is mentioned. Examples of the other monomer include acrylonitrile, (meth) acrylic acid esters having an alkyl group which may have a hydroxy group having 1 to 22 carbon atoms, preferably 1 to 18 carbon atoms, and an aromatic other than styrene. And ring-containing monomers. The alkyl (meth) acrylate macromonomer having a polymerizable functional group at one end is an alkyl (meth) acrylate homopolymer having a polymerizable functional group at one end and an alkyl (meth) having a polymerizable functional group at one end. Examples thereof include copolymers of (meth) acrylate and other monomers. Preferably it is a C1-C8 alkyl (meth) acrylate macromonomer, for example, a methyl methacrylate macromonomer, a butyl acrylate macromonomer, an isobutyl methacrylate macromonomer, etc. are mentioned.

  (C) The number average molecular weight of the macromonomer is preferably 1,000 to 10,000, and preferably 2,000 to 8,000 from the viewpoint of keeping the viscosity low while increasing the copolymerization ratio in order to increase the dispersion stability. Is more preferable.

  (D) As a hydrophobic monomer, the (meth) acrylate which has an alkyl group, or an aromatic group containing monomer is mentioned. Examples of the (meth) acrylate having an alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, 2-ethylhexyl (meth) ) Acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, behenyl (meth) acrylate, and the like. . Examples of the aromatic group-containing monomer include styrene, vinyl naphthalene, α-methyl styrene, vinyl toluene, ethyl vinyl benzene, 4-vinyl biphenyl, 1,1-diphenyl ethylene, and the like. Among these, styrene, α-methylstyrene, and vinyltoluene are more preferable from the viewpoint of scratch resistance and storage stability. Said (d) hydrophobic monomer can be used individually or in combination of 2 or more types.

  (E) As the hydroxyl group-containing monomer, for example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethylene glycol (n = 2 to 30, n represents the average number of added moles of oxyalkylene group) The same shall apply hereinafter.) (Meth) acrylate, polypropylene glycol (n = 2 to 30) (meth) acrylate, poly (ethylene glycol (n = 1 to 15) / propylene glycol (n = 1 to 15)) (meth) acrylate Polyethylene glycol methacrylate 2-ethylhexyl ether and the like. Among these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, polyethylene glycol methacrylate 2-ethylhexyl ether, and polypropylene glycol methacrylate are more preferable.

  The (e) hydroxyl group-containing monomer can be used alone or in combination of two or more.

  (F) Examples of the oxyalkylene group-containing monomer include (meth) acrylate, methoxypolytetramethylene glycol (p = 1 to 30) (meth) acrylate, ethoxypolyethylene glycol (p = 1 to 30) (meth) acrylate, ( Iso) propoxypolyethylene glycol (p = 1-30) (meth) acrylate, butoxypolyethylene glycol (p = 1-30) (meth) acrylate, octoxypolyethylene glycol (p = 1-30) (meth) acrylate, phenoxypolyethylene Glycol (p = 1-30) (meth) acrylate, methoxypolypropylene glycol (p = 1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) (p = 1-30, ethylene glycol therein) Call part to 29) (meth) acrylate, phenoxy (ethylene glycol-propylene glycol copolymer) (p = 1 to 30, ethylene glycol moieties therein 1 to 29) (meth) acrylate. Here, p is the average added mole number of alkylene glycol constituting a part of the oxyalkylene group-containing monomer. The said (f) oxyalkylene group containing monomer can be used individually or in combination of 2 or more types.

  The blending ratio of each monomer used in the binder resin is preferably 10 to 80% by weight, more preferably 25 to 80% by weight of the (a) aromatic group-containing (meth) acrylate monomer based on the amount of all monomers used. %, Particularly preferably in the range of 25 to 75% by weight. (B) The salt-forming group-containing monomer is preferably in the range of 3 to 30% by weight, more preferably 5 to 25% by weight, and particularly preferably 5 to 20% by weight. The content of the (c) macromonomer is preferably in the range of 0 to 50% by weight, more preferably 5 to 35% by weight, and particularly preferably 5 to 30% by weight. (D) Content of hydrophobic monomer becomes like this. Preferably it is 0 to 40 weight%, More preferably, it is the range of 0 to 20 weight%. (E) Content of a hydroxyl-containing monomer becomes like this. Preferably it is 0 to 40 weight%, More preferably, it is the range of 0 to 20 weight%. (F) The content of the oxyalkylene group-containing monomer is preferably 0 to 50% by weight, more preferably 10 to 40% by weight.

  The binder resin contains (a) an aromatic group-containing (meth) acrylate monomer in the presence of a surfactant and / or a reactive surfactant, and (b) a salt-forming group-containing monomer as necessary. It is obtained by elongation polymerization of (c) a macromonomer, (d) a hydrophobic monomer, (e) a hydroxyl group-containing monomer, (f) an oxyalkylene group-containing monomer, or a monomer mixture containing at least two of these. It is a polymer emulsion.

  Reactive surfactants have one or more unsaturated double bonds that can be radically polymerized in the molecule and have excellent monomer emulsifying properties, making them useful for the production of highly stable polymer emulsions. is there.

  As the reactive surfactant, at least one of hydrophobic groups such as a linear or branched alkyl group or alkenyl group having 8 to 30, preferably 12 to 22 carbon atoms, an ionic group, An anionic or nonionic group having at least one of hydrophilic groups such as an oxyalkylene group is preferred.

  Specific examples of the reactive surfactant include Latemul S-120P, S-180A (manufactured by Kao Corporation), and Eleminol JS-2 (manufactured by Sanyo Kasei Co., Ltd.) in the sulfosuccinate ester system. Examples of alkylphenol ethers include Aqualon HS-10 and RN-20 (Daiichi Kogyo Seiyaku Co., Ltd.).

  For the polymerization reaction of the monomer, a polymerization initiator such as persulfate such as potassium persulfate or hydrogen peroxide can be used in addition to the reactive surfactant. The dispersion of the binder resin synthesized with the above monomer is in the range of 0.5 to 15% by weight, more preferably 1 to 10% by weight, and most preferably 2 to 8% by weight, based on the whole ink for inkjet printing. It is blended with.

  The binder resin particles may be hollow particles. Binder resin hollow particles can be produced by preparing binder resin particles by an elongation polymerization method, which will be described later, and then subjecting the binder resin particles to a base swelling method or the like. By making the binder resin particles hollow particles, the binder resin particles can be prevented from settling in the ink, and the storage stability of the ink for inkjet printing can be improved.

(Coloring agent)
The colorant contained in the ink for inkjet printing is not particularly limited as long as it is insoluble in the vehicle, and various colorants can be employed depending on the purpose. Specific colorants include, for example, organic pigments, inorganic pigments, oil-soluble dyes, disperse dyes, oxidation dyes, reactive dyes, titanium oxide, magnetic particles, alumina, silica, ceramics, carbon black, metal nanoparticles, and organic metals. And at least one kind of particles selected from the group consisting of: Examples of the metal nanoparticle material include gold, silver, copper, and aluminum. In the case of titanium oxide, it can be suitably used as a white paint.

  Examples of the pigment include carbon black as a black pigment. Examples of color pigments include anthraquinone, phthalocyanine blue, phthalocyanine green, diazo, monoazo, pyranthrone, perylene, heterocyclic yellow, quinacridone, and (thio) indigoid. Representative examples of phthalocyanine blue include copper phthalocyanine blue and its derivatives (Pigment Blue 15). Representative examples of quinacridone include Pigment Orange 48, Pigment Orange 49, Pigment Red 122, Pigment Red 192, Pigment Red 202, Pigment Red 206, Pigment Red 207, Pigment Red 209, Pigment Violet 19 and Pigment Violet 42. Representative examples of anthraquinones include pigment red 43, pigment red 194 (perinone red), pigment red 216 (brominated pyrantrone red) and pigment red 226 (pyrantron red). Representative examples of pyrerin include Pigment Red 123 (Bell Million), Pigment Red 149 (Scarlet), Pigment Red 179 (Maroon), Pigment Red 190 (Red), Pigment Violet, Pigment Red 189 (Yellow Shade Red) and Pigment. Includes red 224. Representative examples of thioindigoid include Pigment Red 86, Pigment Red 87, Pigment Red 88, Pigment Red 181, Pigment Red 198, Pigment Violet 36 and Pigment Violet 38. Representative examples of heterocyclic yellow include pigment yellow 117 and pigment yellow 138. Examples of other suitable pigments are described in the reference (The Color Index 3rd edition (The Society of Dyers and Colorists, 1982)).

  When a dye is used as the colorant, an oil-soluble dye and a disperse dye are preferably used from the viewpoint of good adsorption / encapsulation.

  Content of a coloring agent is mix | blended in the range of 1-20 weight% with respect to the whole ink for inkjet printing, Preferably it is 2-13 weight%, Most preferably, it is the range of 3-10 weight%.

  As the colorant, it is possible to use a colorant in which at least one hydrophilic group is bonded to the surface directly or through another atomic group and can be stably dispersed without using a dispersant. . As the colorant having a hydrophilic group introduced on the surface, those having ionicity are preferred, and those having an anionic charge or those having a cationic charge can be suitably used.

  In the case of using a dispersant that disperses the colorant, for example, an anionic dispersant, a polymer-type dispersant, and a nonionic dispersant may be used.

  Anionic dispersants include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene monostyryl phenyl ether sulfate, polyoxyethylene distyryl phenyl ether sulfate, polyoxyethylene alkyl ether phosphate Salt, polyoxyethylene alkyl phenyl ether phosphate, polyoxyethylene monostyryl phenyl ether phosphate, polyoxyethylene distyryl phenyl ether phosphate, polyoxyethylene alkyl ether carboxylate, polyoxyethylene alkyl phenyl ether carboxyl Acid salts and the like are preferably used.

  Polymeric dispersants include polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer A coalescence or the like is preferably used.

  Nonionic dispersants include polyoxyethylene lauryl ether, polyoxyethylene myristyl ether, polyoxyethylene alkyl ethers such as polyoxyethylene oleyl ether, polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octylphenyl ether, polyoxyethylene α Naphthyl ether, polyoxyethylene polyoxypropylene block copolymer and the like are preferably used.

  The HLB of the nonionic dispersant is preferably from 12 to 19.5, more preferably from 13 to 19. By using a nonionic dispersant having an HLB of 12 or more, the familiarity of the dispersant with the dispersion medium is improved, and the dispersion stability is improved. Further, by using a nonionic dispersant having an HLB of 19.5 or less, the dispersant is easily adsorbed to the colorant, and the dispersion stability is improved.

  Further, for example, a cationic dispersant having a quaternary ammonium group can also be used.

  The addition amount of the dispersant is preferably 10% by weight or more and 50% by weight or less of the pigment. By making the addition amount of the dispersant 10% by weight or more of the pigment, the storage stability of the colorant dispersion and the ink can be maintained, and the time for dispersion can be shortened.

  The polymer-type, nonionic-type and anionic-type colorant dispersants can be used alone or in combination of two or more, depending on the purpose.

(solvent)
Examples of the solvent include water and a hydrophilic solvent.

  The water content in the ink for inkjet printing may be appropriately set according to the purpose of printing, etc., but is preferably 50% by weight or more, more preferably 60% by weight or more, and most preferably based on the total amount of ink. Is 70% by weight or more. The ink for inkjet printing according to the present embodiment preferably has a high water content as compared with a normal water-based inkjet printing ink. The reason is to provide an eco ink that reduces the environmental load.

  Specific examples of the hydrophilic solvent include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, propylene, and the like. Examples include carbonate, ethylene carbonate, trimethylolpropane, tetramethylurea and urea.

  Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, polyethylene glycol, polypropylene glycol, 1,3-butanediol, 3-methyl-1, 3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol, 1,2,6-hexanetriol, 1,2,4- Examples include butanetriol, 1,2,3-butanetriol, 2-methyl-2,4-pentanediol, petriol, and 3-methoxy-3-methyl-1-butanediol.

  Examples of the polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether and the like.

  Examples of the polyhydric alcohol aryl ethers include polyvalent polyols such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, diethylene glycol isobutyl ether, triethylene glycol isobutyl ether, and diethylene glycol isopropyl ether. Alcohol aryl ether etc. are mentioned.

  Examples of the nitrogen-containing heterocyclic compound include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone, and the like. .

  Examples of amides include formamide, N-methylformamide, N, N-dimethylformamide and the like.

  Examples of amines include monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, and triethylamine.

  Examples of the sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiethanol, thiodiglycol and the like.

  Among these hydrophilic solvents, especially glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol 1,5-pentanediol, tetraethylene glycol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, polyethylene glycol, 1,2,4-butanetriol, 1,2,6-hexanetriol Thiodiglycol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are more preferred. These hydrophilic solvents are excellent in solubility and excellent in preventing poor jetting characteristics due to water evaporation.

  The solvent mentioned above can be used individually or in combination of 2 or more types. The content of the hydrophilic solvent may be appropriately set according to the purpose of printing, etc., but is preferably 50% by weight or less, more preferably 40% by weight or less, and most preferably 30% by weight with respect to the total amount of ink. % Or less.

(Other ingredients)
In addition, inks for inkjet printing include antifungal agents, rust inhibitors, pH adjusters, wetting agents, antifoaming agents, surfactants, water-soluble ultraviolet absorbers, water-soluble infrared rays as additives other than the components described so far. You may further contain components, such as an absorber. The surfactant can be used to improve the dispersibility of the binder resin particles. There is no restriction | limiting in particular in the mixing method of each of these components.

(Other binder resins)
In the case where a metal plating layer is formed on the surface of the binder resin particles, in order to disperse the binder resin particles having the metal plating layer in a solvent and to suitably fix the discharged ink to the recording medium. In addition, the ink for inkjet printing may further contain particles of a binder resin that does not have a metal plating layer. With such binder resin particles, the binder resin particles having the metal plating layer can be dispersed in the solvent, and the binder resin having the metal plating layer is fixed to the recording medium after being fixed to each other. Can be made. The particles of the binder resin are not particularly limited, and the content can be adjusted as appropriate. Further, such binder resin particles can be synthesized using the same monomer as that for forming the binder resin particles described above.

[Method for producing ink for inkjet printing]
An ink-jet printing ink manufacturing method according to an embodiment of the present invention is a manufacturing method for manufacturing an ink-jet printing ink containing a solvent and particles of a binder resin dispersed or suspended in the solvent. It includes a synthesis step of producing the binder resin particles by a polymerization method.

(Synthesis process)
In the synthesis step, binder resin particles are prepared by an extension polymerization method. In the synthesis step, emulsion polymerization in which any of the above-described monomers is emulsified in a solvent while being subjected to a polymerization reaction, and shearing force is applied to the monomer in the emulsion polymerization to form an oval shaped polymer particle.

<Emulsion polymerization>
In the emulsion polymerization of the binder resin particles, for example, a water phase is prepared by blending a reactive surfactant and a polymerization initiator such as potassium persulfate in a solvent heated to a desired temperature. . And an oil phase is prepared by mixing a monomer beforehand. The aqueous phase is heated to a desired temperature, and the monomer is emulsion-polymerized by dropping an oil phase comprising a mixture of the above monomers under stirring conditions. Stirring of the aqueous phase during emulsion polymerization may be performed using a known dispersion apparatus such as a disper mixer, a homomixer, a homogenizer, a high-pressure jet dispersion apparatus, or an ultrasonic dispersion apparatus.

  In the case where the colorant is encapsulated in the binder resin particles, the colorant may be previously dispersed in the above-described monomer by a dispersing device such as a bead mill in the previous stage of emulsion polymerization.

  Further, when dispersing the colorant in the solvent, the above-mentioned dispersant and colorant are added to the solvent, the colorant is dispersed using a dispersing device such as a bead mill, and the binder resin particles are synthesized and then the colorant. The dispersion liquid and binder resin particles may be blended.

  The glass transition temperature (Tg) of the emulsion-polymerized binder resin particles is preferably in the range of 50 ° C. or higher and 180 ° C. or lower. By setting the glass transition temperature within the above range, the shape of the binder resin particles can be suitably flattened in the modification described later.

<Variation>
In the modification of the binder resin particles, the binder resin particles during or after emulsion polymerization are flattened to form flat particles having at least one elliptical cross section. In the modification, the binder resin particles are flattened by applying a shearing force to the binder resin particles during or after the emulsion polymerization using a homomixer or the like. In the modification, all of the binder resin particles in the solvent may not be flattened, and may contain partially spherical binder resin particles. For example, the flat particles may be contained in an amount of 20 wt% or more and 100 wt% or less with respect to the total amount of the binder resin particles in the solvent.

  In addition, by modifying the temperature of the wall surface inside the stator of the homomixer and the temperature of the dispersion of the binder resin particles in the modification, the modification can be performed under conditions suitable for the glass transition temperature of the binder resin particles. it can.

(Other processes)
In the method for producing ink for inkjet printing, after the binder resin synthesis step, if necessary, a coloring agent dispersion, a penetrant, a surfactant for improving the dispersibility of the binder resin, and the like are blended. Thus, an ink for inkjet printing can be produced. Furthermore, the manufactured ink for ink jet printing may further contain components such as an antifungal agent, an antirust agent, a pH adjuster, a wetting agent, an antifoaming agent, a water-soluble ultraviolet absorber, and a water-soluble infrared absorber as necessary. It can also be blended.

  As described above, since the method for producing the ink for inkjet printing according to the present embodiment synthesizes the binder resin particles by the extension polymerization method, it is possible to suitably produce flat binder resin particles. Ink for ink jet printing capable of reducing irregularities generated on the surface of the ink layer on the recording medium can be suitably produced.

(Electroless plating process)
The ink jet printing ink production method may further include an electroless plating step of electrolessly plating the surface of the binder resin particles after the synthesis step. In the electroless plating step, a metal plating layer is formed on the surface of the binder resin particles produced in the synthesis step. By forming a metal plating layer on the surface of the binder resin particles, a metallic color ink for ink jet printing can be produced. At this time, the ink for inkjet printing further contains a binder resin particle having no metal plating layer in the solvent, thereby dispersibility of the binder resin particles having the metal plating layer in the metallic ink, and The fixing property of the ink on the recording medium can be improved.

  In the electroless plating step, for example, a metal such as Ni, Al, Cu, Ag, or Au can be electrolessly plated on the surface of the binder resin particles by a known electroless plating method. In the electroless plating process, binder resin particles are mixed into such an acidic solution of metal, and a reducing agent such as hypophosphorous acid and hydrazine is added to form a metal plating layer on the surface of the binder resin particles. It may be formed. The electroless plating step may be performed after removing the solvent from the binder resin particle dispersion prepared in the synthesis step and washing and drying the binder resin particles.

  In the electroless plating step, a metal plating layer is formed on spherical binder resin particles that have not been deformed, and the binder resin particles are mixed with a dispersion of flat particles produced by the synthesis step described above. Metallic ink-jet printing inks may be manufactured.

  Moreover, in the ink for inkjet printing containing the particle | grains of binder resin which formed the metal plating layer in the electroless-plating process, you may manufacture a metallic ink of a desired color by adding a coloring agent further to a solvent.

[Printing method]
A printing method using the ink for inkjet printing according to the present invention also belongs to the scope of the present invention.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

(Additional notes)
The ink for inkjet printing according to the present invention contains a solvent and particles of a binder resin dispersed or suspended in the solvent, and the particles of the binder resin include flat particles 1 having at least one elliptical cross section. .

  According to the above configuration, the particles of the binder resin contained in the ink include the flat particles 1 having at least one elliptical cross section. Therefore, when such ink lands on the recording medium 10, the long axis that is the longest diameter among the diameters passing through the center of gravity of the flat particles 1 on the surface of the recording medium 10 is the recording medium 10. The flat particles 1 fall down along the surface. That is, in the ink layer 20 formed on the recording medium 10, the flat particles 1 are oriented so that their long axes are along the surface of the recording medium 10.

  For this reason, it is possible to reduce the level difference of the irregularities generated on the surface of the ink layer 20 on the recording medium 10 due to the shape of the binder resin particles. As a result, light scattering caused by unevenness on the surface of the ink layer 20 can be reduced, so that a highly glossy printed matter can be obtained.

  In the ink for ink jet printing according to the present invention, the flat particles 1 are produced by an extension polymerization method.

  According to the said structure, since the flat particle 1 is produced by the extension | elongation polymerization method, the ink for inkjet printing containing the flat particle 1 suitably flattened is obtained efficiently.

  In the ink for inkjet printing according to the present invention, the flat particle 1 has a longest diameter of 1.5 to 15 times the shortest diameter among the diameters passing through the center of gravity. is there.

  According to the said structure, in the flat particle 1, the length of the long axis which is the longest diameter among the diameters which pass through the gravity center becomes sufficiently longer than the length of the short axis which is the shortest diameter. Thereby, the flat particles 1 in the ink that has landed on the recording medium 10 are likely to fall on the recording medium 10, and the flat particles 1 can be easily formed so that the long axis of the flat particles 1 is along the surface of the recording medium. Oriented to Accordingly, it is possible to more effectively reduce the level difference of the unevenness generated on the surface of the ink layer 20.

  In the ink for inkjet printing according to the present invention, the flat particles contain the colorant 2.

  According to the said structure, since the coloring agent 2 is included in the said flat particle, aggregation of the coloring agent 2 can be prevented and the preservability and discharge stability of an ink can be improved.

  In the ink for ink-jet printing according to the present invention, the flat particles 1 further include particles of a binder resin that includes a metal plating layer on the particle surface and does not have a metal plating layer.

  According to the above configuration, a suitable metallic ink can be provided. Further, since the flat particles 1 provided with the metal plating layer are oriented along the surface of the recording medium 10, printing with such an ink makes it possible to obtain a printed matter with excellent concealment of the ink layer 20. can get.

  The ink for inkjet printing which concerns on this invention contains the said flat particle 1 20weight% or more and 100 weight% or less with respect to the total amount of the particle | grains of the said binder resin.

  When the ink for inkjet printing contains the flat particles 1 with the content in the above range, the unevenness generated on the surface of the ink layer 20 due to the shape of the particles of the binder resin even if the particles of the other binder resin are spherical. The height difference can be reduced.

  A method for producing an ink for ink-jet printing according to the present invention is a method for producing an ink for ink-jet printing containing a solvent and particles of a binder resin dispersed or suspended in the solvent. A synthesis process for producing binder resin particles is included.

  According to the above configuration, since the particles of the flat binder resin can be suitably produced by the extension polymerization method, the unevenness generated on the surface of the ink layer 20 on the recording medium 10 can be reduced. An ink can be suitably manufactured.

  The ink jet printing ink production method according to the present invention further includes an electroless plating step of electrolessly plating the surface of the binder resin particles after the synthesis step.

  According to the said structure, a metal plating layer can be formed in the surface of the particle | grains of the flat binder resin produced by the extending | stretching polymerization method. Thereby, the metallic ink for inkjet printing can be manufactured suitably.

  The printing method according to the present invention uses any one of the above ink jet printing inks.

  According to the said structure, highly glossy printed matter can be obtained using the ink for inkjet printing which concerns on this invention.

  The present invention can be used for inkjet printing.

DESCRIPTION OF SYMBOLS 1 Flat particle 2 Colorant 10 Recording medium 20 Ink layer

Claims (9)

Containing a solvent and particles of a binder resin dispersed or suspended in the solvent,
The ink for inkjet printing, wherein the binder resin particles include flat particles having at least one elliptical cross section.   2. The ink for ink jet printing according to claim 1, wherein the flat particles are produced by an extension polymerization method.   The flat particle has a length of the longest diameter among diameters passing through the center of gravity of the flat particle, which is 1.5 times or more and 15 times or less of the length of the shortest diameter. Ink for ink-jet printing as described in 1.   The ink for inkjet printing according to any one of claims 1 to 3, wherein the flat particles contain a colorant. The flat particles have a metal plating layer on the particle surface,
The ink for inkjet printing according to any one of claims 1 to 4, further comprising particles of a binder resin that does not have a metal plating layer.   The ink for inkjet printing according to any one of claims 1 to 5, wherein the flat particles are contained in an amount of 20% by weight to 100% by weight with respect to a total amount of the particles of the binder resin. A production method for producing an ink for inkjet printing comprising a solvent and particles of a binder resin dispersed or suspended in the solvent,
A method for producing an ink for inkjet printing, comprising a synthesis step of producing particles of the binder resin by an elongation polymerization method.   The method for producing ink for inkjet printing according to claim 7, further comprising an electroless plating step of electrolessly plating the surface of the binder resin particles after the synthesis step.   An ink jet printing method using the ink for ink jet printing according to any one of claims 1 to 6.

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